Anyone who exercises regularly has probably experienced a muscle cramp or seen someone else deal with one during training or competition. Although they are very common, there are still many myths about what actually causes them.
For many years, dehydration or electrolyte deficiency was believed to be the primary cause of exercise-related muscle cramps. Today, research shows that the explanation is much more complex and involves factors related to neuromuscular function, fatigue, and each athlete's individual characteristics.
What are muscle cramps?
Exercise-associated muscle cramps (EAMCs) are involuntary, painful, and temporary muscle contractions that typically occur during or immediately after intense physical activity.
They most often affect muscles that work repeatedly, such as the calves, hamstrings, and quadriceps, especially during endurance sports like running, cycling, and triathlon.
Although cramps usually resolve within a few minutes, they can negatively impact performance and, in some cases, prevent an athlete from finishing a race.
Why are some athletes more prone to muscle cramps?
There is no single cause. In most cases, several factors occur simultaneously.
1. Greater muscle fatigue
The most widely accepted explanation today is that fatigue alters the way the nervous system controls muscle contractions.
When muscles become highly fatigued, the balance between signals that promote muscle contraction and those responsible for muscle relaxation is disrupted. This increases motor neuron excitability, making muscle cramps more likely.
This is why cramps often occur during the final stages of long-distance races or when exercise intensity exceeds an athlete's current fitness level.
2. Insufficient physical conditioning
Two athletes may compete in the same event, but the less well-trained athlete is more likely to reach higher levels of fatigue.
This helps explain why beginners or athletes who rapidly increase their training volume or intensity often experience more muscle cramps.
Progressive training and proper physical conditioning are key strategies for reducing this risk.
3. High sodium losses through sweat
Although sodium deficiency is no longer considered the sole cause of muscle cramps, excessive sodium loss may contribute in certain situations.
Athletes with high sweat rates or significant sodium losses during prolonged exercise may experience changes in fluid balance and neuromuscular function.
This factor appears to be particularly important during long-duration events performed in hot and humid environments.
4. Inadequate hydration strategies
Both dehydration and excessive water intake without adequate electrolyte replacement can disrupt the body's fluid balance.
In addition to increasing physiological stress during exercise, poor hydration may contribute to fatigue-related mechanisms associated with muscle cramps. In more severe cases, it may also increase the risk of exercise-associated hyponatremia.
For this reason, hydration strategies should be individualized according to exercise duration, environmental conditions, and each athlete's needs.
5. Exercising beyond current fitness level
Participating in a race that is longer than usual or performing high-intensity exercise without adequate preparation significantly increases the likelihood of muscle cramps.
In most cases, the issue is not a single nutrient deficiency but rather the combination of excessive effort and accumulated fatigue.
Can muscle cramps be prevented?
Although it is impossible to eliminate the risk completely, several strategies may help reduce the likelihood of exercise-associated muscle cramps:
- Follow a progressive and well-structured training program.
- Develop an individualized hydration plan.
- Replace electrolytes, especially sodium, during prolonged exercise when appropriate.
- Consume adequate amounts of carbohydrates during long events to delay fatigue.
- Prioritize recovery between demanding training sessions.
- Gradually acclimate to exercising in hot environments before competition.
The role of hydration and electrolytes
Not every muscle cramp is caused by sodium deficiency, but that does not mean electrolyte replacement is unnecessary.
For athletes with high sweat rates, particularly during exercise lasting longer than one hour and performed in hot conditions, sodium replacement strategies may help maintain fluid balance and support performance.
The key point is that hydration, carbohydrate intake, appropriate training, and recovery should all work together to reduce excessive fatigue and, consequently, the likelihood of muscle cramps.
Conclusion
Exercise-associated muscle cramps do not have a single cause. Current evidence suggests that neuromuscular fatigue is the primary mechanism involved, while factors such as physical conditioning, exercise intensity, hydration status, and electrolyte replacement can either increase or decrease an athlete's risk.
Rather than looking for a single solution, athletes should focus on appropriate training, individualized nutrition strategies, and personalized hydration plans to minimize the risk of muscle cramps.
